A lot of people have formal education, but I don't think it is always necessary. With some practice and self-learning, you can become a great UI/ UX designer!
I highly recommend the book "The Design of Everyday Things" by Don Norman.
An absolute classic! Talks about core concepts such as user-centered design.

Even better than reading the book, join the following event to learn from the master Don Norman himself on Dec 17, 2013. In Silicon Valley. Details here: http://www.meetup.com/Igniter/events/142264152/